1. Bubble-assisted Liquid Hole Multipliers in LXe and LAr: towards “local dual-phase TPCs”
E. Erdal(1), L. Arazi(2), A. Breskin(1), S. Shchemelinin(1), A. Roy(2), A. Tesi(1), D. Vartsky(1), and S. Bressler(1)
(1) Dept. of Astrophysics & Particle Physics, Weizmann Institute of Science, Israel
(2) Unit of Nuclear Engineering, Faculty of Engineering Sciences, Ben-Gurion University of the Negev, Israel
LIDINE 2019
Manchester, August 2019

2. Hole-electrodes Gas Electron Multiplier GEM
Thick Gas Electron Multiplier - THGEM (a.k.a. LEM)

3. New concept: generating electroluminescence in a bubble
“hole-electrode” 𝐸
𝑉 𝑡𝑜𝑝
𝑉 𝑏𝑜𝑡𝑡𝑜𝑚
VUV photon
𝑒 −
𝑒 −
Cs I
Resistive wires
Light readout (e.g. PMT , SiPM)
Noble liquid (LXe / LAr)
L. Arazi et al JINST 10 P08015 [arXiv: ] & E. Erdal et al JINST 10 P [arXiv: ]

4. Small Liquid Xenon Cryostat
CAMERA
E. Erdal et al JINST 10 P [arXiv: ]

5. Bubble Inflation
E. Erdal et al JINST 10 P [arXiv: ]

6. Combined light and charge readout
1 𝑒 −  flash of ~400 VUV photons
E. Erdal et al JINST 13 P [arXiv: ]

7. Response of different electrodes
E. Erdal et al JINST 13 P [arXiv: ]

8. Charge multiplication in the bubble
Apply strong electric field between bottom of electrode and wires
E. Erdal et al JINST 13 P [arXiv: ]

9. Image of 241Am source with pixelated readout
LHM reconstruction
3.9mm dia.
Resolution: σ≈200 μm
E. Erdal et al JINST 14 P [arXiv: ]

10. NEW: It works also in Liquid Argon!
Same setup,
No CsI on top of the THGEM: S2 only
arXiv: (to be submitted to JINST)

11. Towards single photon sensing: Effective CsI Quantum Efficiency in LXe
𝐸 – energy of alpha particle
𝑊 𝑠 – mean energy per photon
𝑓 – rate of alpha emission into LXe
Ω – solid angle towards photocathode
𝑇 – Mesh transmission
𝐼= 𝐸 𝑊 𝑠 ⋅𝑓⋅ Ω 4𝜋 ⋅𝑇⋅ 𝑒 − ⋅ 𝑄 𝐸 𝑒𝑓𝑓
Similar values measured also by: E. Aprile et al., NIM A 338 (1994)

12. Towards single photon sensing: Effective CsI Quantum Efficiency in LXe
Expected PDE: 𝟏 𝑨 ∫𝑸𝑬 𝑬 𝒙,𝒚 𝒅𝒙 𝒅𝒚
Expected PDE (THGEM): 15%
Measured PDE: ~2%
Expected PDE (GEM , SC-GEM): 22%
Measured PDE: ~4%

13. Where are electrons lost?1
𝑒 − 2
From liquid to gas: 0.69 eV potential barrier
E. Erdal et al JINST 13 P [arXiv: ]

14. What is the shape of the bubble? How does it affect the EL signal?
𝑒 −
Resistive wires
Light readout
Noble liquid (LXe / LAr)

15. We have a dream… for large-volume dark-matter detectors
Part of the DARWIN generic R&D program:
Aalbers, J., et al., Journal of Cosmology and Astroparticle Physics, (11): p. 017

16. To conclude Imaging Stable bubble Light and charge detection
Charge gain
Different geometries
Deeper?
Shape of the bubble?
Gliding electrons?

18. Backup slides

19. Boiling on the tip of a wire
E. Erdal et al JINST 10 P [arXiv: ]

20. Bubble breathing
E. Erdal et al JINST 10 P [arXiv: ]

21. Vertical bubbles LXe S1 S2 Bubble 241Am S2 S1 Et Ed To PMT Fine meshα e S2 S1
4 mm
LXe S1
Bubble Et Ed
To PMT S2
Fine mesh
112 µm opening
THGEM
Heating wire

22. S1 dependence on THGEM voltage
L. Arazi et al JINST 10 P08015 [arXiv: ]

23. Electroluminescence “in THGEM holes”
Threshold for electroluminescence:
Vapor 170K): ~ 2-3 kV/cm ††
Liquid: kV/cm †††
Indirect proof of bubble-assisted electroluminescence: killing light by abrupt pressure change. Interpretation: bubbles collapse! ††††
Light 2kV
~ 600 UV photons / electron †
† L. Arazi et al JINST 8 C12004 [arXiv: ]
††C.M.B. Monteiro et al JINST 2 P05001.
††† T. Doke, Nucl. Intrum. Meth. 196 (1982).
†††† L. Arazi et al JINST 10 P08015 [arXiv: ].

24. ‘Classical’ dual-phase Time Projection Chamber
Top PMTs
anode
GXe
𝑆 2 𝑆 1 𝑛𝑢𝑐𝑙𝑒𝑎𝑟 𝑟𝑒𝑐𝑜𝑖𝑙
𝑆 2 𝑆 1 𝑒𝑙𝑒𝑐𝑡𝑟𝑜𝑛 𝑟𝑒𝑐𝑜𝑖𝑙
Signal
Background
<
Hit pattern on top PMT array  x,y
Time difference 𝑡 2 − 𝑡 1  z
S2/S1  background discrimination
~1 kV/cm
~10 kV/cm
gate
LXe
cathode
Dark matter particle
Bottom PMTs
Aalbers, J. et al., Journal of Cosmology and Astroparticle Physics, (11): p. 017

25. Scaling up of ‘traditional’ dual-phase TPC
Top PMTs
𝑆 2 ∝ 𝑁 𝑒 𝑑 𝑔𝑎𝑠 𝐸/𝜌 −𝑐𝑜𝑛𝑠𝑡
anode
GXe
1 kV/cm
10 kV/cm
gate S2 S2
S2 ≠ S2
LXe
cathode
Degradation of signal / noise ratio
Bottom PMTs
Aalbers, J. et al., Journal of Cosmology and Astroparticle Physics, (11): p. 017